Isolation structure integrated with semiconductor device and manufacturing method thereof

ABSTRACT

A method for manufacturing an isolation structure integrated with semiconductor device includes following steps. A substrate is provided. A plurality of trenched gates is formed in the substrate. A first insulating layer and a second insulating layer are sequentially deposited on the substrate. A first etching process is performed to remove portions of the second insulating layer to expose portions of the first insulating layer. A second etching process is then performed to remove the exposed second insulating layer to expose the trenched gates and to define at least an active region.

This application claims priority to Taiwanese Patent Application SerialNo. 103139109, filed on Nov. 11, 2014, the entire disclosures of whichare hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an isolation structure and a semiconductordevice and a manufacturing method thereof, and more particularly, to anisolation structure integrated with a semiconductor device and amanufacturing method.

2. Description of the Prior Art

In recent years, along with the trend for achieving higher packingdensity in integrated circuit semiconductor devices, active research anddevelopment have been in progress, striving for device miniaturization.Furthermore, isolation regions, which are necessary to prevent currentshort between devices, taking up a considerable portion of a chip, isbecome more and more important due to the device miniaturization.

Conventionally, the LOCOS (local oxidation of silicon) method has beengenerally utilized as one of the techniques for forming isolationregions on a substrate. And the conventional process for forming anisolation structure by the LOCOS method is to form a pad oxide layerover a silicon substrate, and a hard mask is then formed thereon. Thehard mask and the pad oxide layer are patterned to define location andsize of the isolation structure(s) to be formed. Next, the siliconsubstrate is placed in a high temperature environment with reaction gassuch as oxygen, and an oxidation is performed to form field oxide(hereinafter abbreviated as FOX) layers. The FOX layers are used todefine active regions on the silicon substrate and to provide electricalisolation between those active regions.

Although FOX layers presently provide many advantages in semiconductortechnology, there are still several problems created by theirapplication to a ULSI circuit die, including “birds' beak” effect. The“bird's beak” effect results from the lateral oxidation under edge ofthe patterned mask and pad oxide layer. The presence of the bird's beakeffectively increases the size of the FOX layers, thereby ultimatelydecreasing the amount of silicon real estate available for later deviceformation. Furthermore, since LOCOS method needs high temperature, timefor performing LOCOS method or forming the FOX layers must be at thebeginning of the whole manufacturing steps, otherwise devices formed onthe substrate are severely impacted.

Therefore, an isolation structure that is able to provide sufficientelectrical isolation, avoid birds' beak effect, and reduce siliconconsumption is still in need.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, a method formanufacturing an isolation structure integrated with a semiconductordevice is provided. According to the method, a substrate is provided anda plurality of trenched gates is then formed in the substrate. Afterforming the trenched gates, a first insulating layer and a secondinsulating layer are sequentially formed on the substrate. Next, a firstetching process is performed to remove portions of the second insulatinglayer to expose portions of the first insulating layer. Then, a secondetching process is performed to remove the exposed first insulatinglayer to expose the trenched gates and to define at least an activeregion.

According to an aspect of the present invention, an isolation structureintegrated with a semiconductor device is provided. The isolationstructure integrated with the semiconductor device includes a substratecomprising a front side and a back side, a plurality of trenched gatesformed in the substrate, and an isolation structure formed in the frontside of the substrate. The isolation structure includes a firstinsulating layer and a second insulating layer, and a bottom surface ofthe isolation structure is higher than top surfaces of the trenchedgates.

According to the isolation integrated with the semiconductor device andmanufacturing method provided by present invention, the isolationstructure used to define the active region and provide electricalisolation are formed by depositions after forming the trenched gates.Since the isolation structure is no longer formed by LOCOS method,high-temperature process is not required. Therefore the isolationstructure can be formed at other time point, instead of the beginningthe whole manufacturing process. And thus process flexibility isimproved. More important, because the isolation structure is formed onthe substrate by depositions, silicon consumption and birds' beak effectto the substrate are all avoided.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-10 are drawings illustrating a method for manufacturing anisolation structure integrated with a semiconductor device provided by apreferred embodiment of the present invention, wherein

FIG. 2 is a schematic drawing in a step subsequent to FIG. 1,

FIG. 3 is a schematic drawing in a step subsequent to FIG. 2,

FIG. 4 is a schematic drawing in a step subsequent to FIG. 3,

FIG. 5 is a schematic drawing in a step subsequent to FIG. 4,

FIG. 6 is a schematic drawing in a step subsequent to FIG. 5,

FIG. 7 is a schematic drawing in a step subsequent to FIG. 6,

FIG. 8 is a schematic drawing in a step subsequent to FIG. 7,

FIG. 9 is a schematic drawing in a step subsequent to FIG. 8, and

FIG. 10 is a schematic drawing in a step subsequent to FIG. 9.

DETAILED DESCRIPTION

Please refer to FIGS. 1-10 which are drawings illustrating a method formanufacturing an isolation structure integrated with a semiconductordevice provided by a preferred embodiment of the present invention. Asshown in FIG. 1, a substrate 100 is provided. The substrate 100 includesa first conductivity type, and the first conductivity is an n type inthe preferred embodiment. The substrate 100 can include a heavily-dopedn-region 100N and an n-typed epitaxial layer 100E formed on theheavily-doped n-region 100N. Furthermore, the substrate 100 includes afront side 100 a and a back side 100 b opposite to the front side 100 a.As shown in FIG. 1, the front side 100 a of the substrate 100 is asurface of the n-typed epitaxial layer 100E. Next, a pad layer 102 and apatterned hard mask 104 are formed on the front side 100 a of thesubstrate 100. According to the preferred embodiment, the pad layer 102can include silicon oxide and the patterned hard mask 104 can includesilicon nitride, but not limited to this. As shown in FIG. 1, thepatterned hard mask 104 is used to define locations and sizes of aplurality of trenches. Subsequently, a proper etching process isperformed to etch the pad layer 102 and the substrate 100 through thepatterned hard mask 104 to form the plurality of the trenches 110 in thesubstrate 100, particularly in the n-typed epitaxial layer 100E. Thetrenches 110 can be arranged in concentric circles, or in a straightline. It is noteworthy that the number, the size and the location of thetrenches 110 are all exemplarily shown in FIG. 1, but not limited tothis.

Please refer to FIG. 2. Next, the patterned hard mask 104 is removed andfollowed by sequentially forming a gate dielectric layer 122 and a gateconductive layer 124 in each trench 110, and the trenches 110 are filledup with the gate conductive layer 124. Consequently, a plurality oftrenched gate 120 is formed in the trenches 110, respectively. It isnoteworthy that, according to the preferred embodiment, an etching backprocess is performed to the gate conductive layer 124 after forming thetrenched gates 120. Consequently, top surfaces of the trenched gates120, that are the top surfaces of the gate conductive layers 124 in thetrenches 110, are all lower than the openings of trenches 110 as shownin FIG. 2.

Please refer to FIG. 2. After forming the trenched gates 120, depositionprocesses are performed to sequentially form a first insulating layer132 and a second insulating layer 134 on the front side 100 a of thesubstrate 100. It should be noted that an etching rate of the firstinsulating layer 132 is different from an etching rate of the pad layer102, and the etching rate of the first insulating layer 132 is alsodifferent from an etching rate of the second insulating layer 134. Forexample, the pad layer 102 includes silicon oxide while the firstinsulating layer 132 includes silicon nitride, which includes etchingrate different from silicon oxide. Furthermore, the second insulatinglayer 134 includes material having etching rate different from siliconnitride, such as silicon oxide, preferably tetraethylorthosilicate(TEOS), but not limited to this. As shown in FIG. 3, the firstinsulating layer 132 is blanketly formed to cover the entire front side100 a of the substrate 100. And thus the trenches 110 are filled up withthe first insulating layer 132. According to the preferred embodiment, athickness of the first insulating layer 132 can be 300 Angstrom (Å) anda thickness of the second insulating layer 134 can be 3000 Å, but notlimited to this.

Please refer to FIG. 4. Subsequently, a first etching process 140 isperformed to remove portions of the second insulating layer 134 and toexpose portions of the first insulating layer 132. The first etchingprocess 140 can be any proper etching process, for example but notlimited to, the first etching process 140 can be a dry etching process.It is noteworthy that since the etching rate of the first insulatinglayer 132 is different from the etching rate of the second insulatinglayer 134, the first insulating layer 132 serves as an etch stop layerin the first etching process 140. In other words, the first insulatinglayer 132 protects the underneath gate dielectric layer 122 and padlayer 102 in the first etching process 140.

Please refer to FIG. 5. After the first etching process 140, a secondetching process 142 is performed to remove the exposed portions of thefirst insulating layer 132 and thus to expose portions of the trenchedgates 120. The second etching process 142 can be any proper etchingprocess, for example but not limited to, the second etching process 142can be a wet etching process. More important, an isolation structure 130is formed on the front side 100 a of the substrate 100, particularly onthe pad layer 102, after the second etching process 142 according to thepreferred embodiment. The isolation structure 130 includes at least thefirst insulating layer 132 and the second insulating layer 134. Becausethe etching rate of the first insulating layer 132 is different from theetching rate of the gate dielectric layer 122 and of the pad layer 102,both of the gate dielectric layer 122 and the pad layer 102 areimperviously to the second etching process 142. More important, theisolation structure 130 defines at least an active region 106 on thesubstrate 100. As shown in FIG. 5, the first insulating layer 132 of theisolation structure 130 is sandwiched between the second insulatinglayer 134 and the pad layer 102. Additionally, because the firstinsulating layer 132 and the second insulating layer 134 of theisolation structure 130 are formed by deposition processes, a bottomsurface of the isolation structure 130, that is a bottom surface of thefirst insulating layer 132, is higher than the top surfaces of thetrenched gates 120, that is the top surfaces of the gate conductivelayers 124.

Please refer to FIG. 6. After performing the second etching process 142,an ion implantation is performed with the isolation structure 130serving as an implant mask. Consequently, abase region 150 is formed inthe substrate 100, particularly formed in the n-typed epitaxial layer100E. The base region 150 includes a second conductivity type, and thesecond conductivity type is complementary with the first conductivitytype. Therefore the base region 150 is a p-based region 150 according tothe preferred embodiment.

Please refer to FIG. 7. Next, a semiconductor layer 160 is formed on thefront side 100 a of the substrate 100 and on the second insulating layer134 of the isolation structure 130. The semiconductor layer 160 is thenpatterned to format least an electrode 162. As shown in FIG. 7, theelectrode 162 strides over the isolation structure 130 and iselectrically connected to one of the trenched gates 120.

Please refer to FIG. 8. After forming the electrode 162 electricallyconnected to one of the trenched gates 120, different ion implantationsare performed to form a plurality of source regions 152 at two sides ofeach trenched gate 120 in the substrate 100, and to form a doped region154 in the base region 150 distal to the electrode 162. The sourceregions 152 include the first conductivity type while the doped region154 includes the second conductivity type. Therefore, the preferredembodiment provides n-source regions 152 and a p-doped region 154. It isalso noteworthy that the heavily-doped n-region 100N is taken as beingformed on the back side 100 b of the substrate 100. More important, theheavily-doped n-region 100N serves as a drain region 156.

Please refer to FIG. 9. After forming the source regions 152 and thedoped region 154, an insulating material layer 170 is formed on thesubstrate 100. The insulating material layer 170 is blanketly formed onthe front side 100 a of the substrate 100, and the trenches 110 arefilled up with the insulating material layer 170. As shown in FIG. 9,the insulating material layer 170 fills the trenches 110, and thuscovers and contacts the top surfaces of the trenched gates 120.Subsequently, the insulating material layer 170 is patterned, and thus aplurality of openings 172 is formed in the insulating material layer170. As shown in FIG. 9, the openings 172 expose at least a portion ofthe electrode 162. More important, the openings 172 expose the sourceregions 152 and the doped region 154 on the front side 100 a of thesubstrate 100. It should be noted that the top surfaces of the trenchedgates 120 are still covered and protected by the insulating materiallayer 170. Next, post-salicide is optionally performed to form silicides(not shown) on silicon surface exposed at bottoms of each opening 172for reducing contact resistance between the substrate 100 and followingformed contacts. However, it should be easily realized by those skilledin the art that the silicide can be formed at different time points.

Please refer to FIG. 10. After forming the openings 172 in theinsulating material layer 170, a metal material is formed on the frontside 100 a of the substrate 100 and followed by planarization.Consequently, a first metal layer 180, a second metal layer 182, and athird metal layer 184 are formed. As shown in FIG. 10, the first metallayer 180 is electrically connected to the source regions 152 and thedoped region 154, the second metal layer 182 is electrically connectedto the electrode 162, and the third metal layer 184 is electricallyconnected to a patterned semiconductor layer 160. Additionally, a fourthmetal layer 186 is formed on the back side 100 b of the substrate 100.And thus a vertical double-diffused MOS (VDMOS) is constructed andobtained according to the preferred embodiment.

According to the isolation integrated with the semiconductor device andmanufacturing method provided by present invention, the isolationstructure used to define the active region(s) and provide electricalisolation is formed by depositions after forming the trenched gates.Since the isolation structure is no longer formed by LOCOS method,high-temperature process is not required. Therefore the isolationstructure can be formed at other time point, instead of the beginningthe whole manufacturing process. And thus process flexibility isimproved. More important, because the isolation structure is formed onthe substrate by depositions, silicon consumption and birds' beak effectto the substrate are all avoided.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. An isolation structure integrated with asemiconductor device comprising: a substrate comprising a front side anda back side; a plurality of trenches formed in the front side of thesubstrate; a trenched gate formed in each of the trenches; an isolationstructure formed on the front side of the substrate, the isolationstructure comprises a first insulating layer and a second insulatinglayer; a plurality of source regions formed on two sides of eachtrenched gate in the substrate; and an insulating material layer,directly covering the isolation structure formed on the substrate,filling up at least some of the trenches, and contacting the topsurfaces of the trenched gates, wherein a bottom surface of theisolation structure is higher than top surfaces of the trenched gates.2. The isolation structure integrated with the semiconductor deviceaccording to claim 1, wherein an etching rate of the first insulatinglayer is different from an etching rate of the second insulating layer.3. The isolation structure integrated with the semiconductor deviceaccording to claim 1, further comprising a pad layer formed on thesubstrate, and the first insulating layer being sandwiched between thesecond insulating layer and the pad layer.
 4. The isolation structureintegrated with the semiconductor device according to claim 1, furthercomprising a first metal layer formed on the front side of thesubstrate, the first metal layer being electrically connected to thesource regions.
 5. The isolation structure integrated with thesemiconductor device according to claim 1, further comprising a drainregion formed at the back side of the substrate.
 6. An isolationstructure integrated with a semiconductor device comprising: a substratecomprising a front side and a back side; a plurality of trenched gatesformed in the substrate; an isolation structure formed on the front sideof the substrate, the isolation structure comprises a first insulatinglayer and a second insulating layer; an electrode formed on the frontside of the substrate, striding over the isolation structure andelectrically connecting to one of the trenched gate; a plurality ofsource regions formed on two sides of each trenched gate in thesubstrate; and an insulating material layer directly covering theisolation structure formed on the substrate, filling up at least some ofthe trenches, and contacting the top surfaces of the trenched gates,wherein a bottom surface of the isolation structure is higher than topsurfaces of the trenched gates.